A new glucose affinity sensor based on a homogeneous fluorescence resonance
energy transfer (FRET) assay system was developed to monitor the competitive binding
between concanavalin A (ConA) and dextran. The FRET quenching kinetics of the
donor were analyzed from frequency-domain (FD) measurements as functions of both
glucose and acceptor-protein concentrations using a Förster-type decay kinetics model.
The results showed that the FD measurements and donor decay kinetics can indicate
quantitative changes in the presence of glucose at concentrations ranging from 0 to 224
mg/dL.
The second set of experiments proved the feasibility of performing analyte
sensing with FD lifetime spectroscopy using microsphere-based sensors in multiple
scattering solutions. A well characterized pH-sensitive fluorophore was entrapped in
poly(ethylene glycol) microspheres. The particles were then immersed in a buffered
polystyrene solution of various pH. Measurements of phase shift and modulation of the
generated and multiply scattered fluorescent light were acquired as the modulation
frequency of the incident excitation light varied from 10 to 120 MHz. After the measured data were analyzed with the coupled diffusion equations, the obtained
lifetimes from the scattering measurements matched values from non-scattering
measurements.
Lastly, a new two-speed Monte Carlo (MC) simulation was developed to predict
light propagation through the sensors and thus was used to evaluate these sensors and to
design these sensors for implantation. The model used random packing structure and
considered geometric optics and two light propagation speeds. Experimental
measurements of phase-shift and modulation of excitation light were made on a cubic
phantom with non-fluorescent resin microspheres of 74 µm diameter, and compared to
those computed from the MC simulation. The results showed that the mean phase shift
(PS) deviation was 0.736° and the mean amplitude deviation was 42%. Quantitative
changes in detected fluorescence phase-shift and modulation were investigated for
microsphere diameter, volume fraction, refractive index, and fluorophore lifetime. We
also found that even though the sensitivity of PS change in the presence of scattering
was the same as the value without scattering, the values of PS were magnified due to the
scattering effects.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1065 |
| Date | 15 May 2009 |
| Creators | Liang, Feng |
| Contributors | Sevick-Muraca, Eva M. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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